Aquaria, particularly the relatively small type for household use, are commonly lit with fluorescent lamps. Former types of fluorescent lamp which have been used, while imparting a not unattractive reddish color to orangy objects such as goldfish, suffers from the disadvantage that, a reddish cast is imparted to almost all colors so that the many varieties of fish now popular for small aquaria do not show up to best advantage. Also there is distortion of green. Furthermore, such types of lamp have the disadvantage of low lumen output, poor lumen maintenance and large color drift with age affecting color rendering.
EP-A-0364124 discloses a fluorescent lamp for use in aquaria, the luminescent layer in said lamp comprising a mixture of red, green and blue phosphors, the red phosphor emitting predominantly in the spectral region of from 610 nm to 620 nm, the green phosphor emitting predominantly in the spectral region of from 540 nm to 545 nm and the blue phosphor having a peak emission wavelength between 430 nm and 480 nm with the half peak width not exceeding 80 nm, said red, green and blue phosphors being blended to form said mixture in such proportions that the color coordinates of the lamp employing said mixture on the CIE chromaticity diagram differ from the point x equals 0.300 and y equals 0.232 in any direction by no more than 10 standard deviations of color matching (SDCM). Most preferably, the lamp of EP-A-0364124 has the color coordinates x equals 0.300 and y equals 0.232.
Individual red, green and blue phosphors which may be used to form the above mixture are well known in the art and according to EP-A124 suitable such phosphors include the following: